Opus reticulatum (also known as reticulated work) is a form of brickwork used in ancient Roman architecture. It consists of diamond-shaped bricks of tuff, referred to as cubilia,[1] placed around a core of opus caementicium.[2] The diamond-shaped tufa blocks were placed with the pointed ends into the cement core at an angle of roughly 45 degrees, so the square bases formed a diagonal pattern, and the pattern of mortar lines resembled a net. Reticulatum is the Latin term for net-like, and opus, the term for a work of art, so the term translates to "net work".

This construction technique was used from the beginning of the 1st century BC, and remained very common until opus latericium, a different form of brickwork, became more common.[2]